OBJECTIVE: The objective of this article was to assess mortality risks at different levels of fasting blood glucose (FBG) in Taiwan, with particular attention to those pre-diabetic subjects with impaired fasting glucose (IFG). RESEARCH DESIGN AND METHODS: Governmental employees and schoolteachers were followed up for an average of 11 years. With the use of Cox regression analyses, mortality risks were calculated for 36,386 subjects, aged 40-69. RESULTS: FBG > or =110 mg/dl was associated with increased mortality risks for all causes, cardiovascular diseases (CVD), and diabetes. IFG, when defined as 110-125 mg/dl, was associated with a significant increase for CVD and/or diabetes mortality. These mortality risks remained elevated when known CVD risk factors were adjusted for. The IFG group shared risk factor characteristics more with the FBG > or =126 mg/dl group than with the FBG <110 mg/dl group. When IFG was defined as 100-125 mg/dl, the number of subjects quadrupled, but mortality risks diminished substantially because of the inclusion of 100-109 mg/dl group. The lowest FBG group, 50-75 mg/dl, had a significant 2-fold risk from all causes. CONCLUSIONS: There was an overall J-shaped relationship between all-cause mortality and FBG. IFG, when defined as 110-125 mg/dl, is an independent risk factor and should be aggressively treated as a disease because its subsequent mortality risks for CVD and diabetes were significantly increased. The newly defined IFG at 100-125 mg/dl did not have the predictive power for later increases in CVD or diabetes mortality.